1. Field of the Invention
The present invention relates to a semiconductor device encapsulant consisting of a resin composition for providing a cured product having a high thermal shock resistance and a high humidity resistance.
2. Description of the Related Art
An epoxy resin composition containing a phenol-novolak resin as a curing agent has been conventionally used as a semiconductor device encapsulant. This resin composition is mainly used as an encapsulant since a cured product of this composition has a high humidity resistance, good high-temperature electrical characteristics, and good molding properties.
In recent years, as semiconductor devices have been more integrated, each functional unit on an element has been more miniatualized and a size of a semiconductor pellet itself has been rapidly increased. Due to such changes in a pellet, conventional encapsulants therefore cannot satisfy requirements such as a high thermal shock resistance. That is, if a conventional epoxy resin composition is used to encapsulate a large pellet having a fine surface structure, a phospho-silicate glass (PSG) film or a silicon nitride (Si.sub.3 N.sub.4) film as a passivation film for an aluminum (Al) pattern formed on the surface of the pellet may crack, or the encapsulating resin may crack. This tendency becomes significant especially when a heat cycle test is conducted. As a result, an outer appearance of a package is degraded or reliability of a semiconductor device is lowered.
In addition, when a surface-mounting type package is soldered, the entire package is exposed to a high-temperature atmosphere at 200.degree. C. to 260.degree. C. for 5 to 90 seconds and subjected to a severe thermal shock. In this case, an encapsulating resin may crack mainly due to vaporization of moisture entrapped in the package.
In order to solve the above problems, a stress applied on an insert by the encapsulating resin must be reduced and the encapsulating resin itself must be strengthened throughout a wide temperature range.
In order to reduce the internal stress of an encapsulating resin, a so-called sea-island structure in which silicone oil or natural rubber is finely dispersed in a resin matrix is assumed to be effective. Actually, this method can considerably reduce the internal stress of an encapsulating resin. This method, however, has a problem of inevitably reducing the strength of the encapsulating resin and has almost no effect of preventing cracks of the encapsulating resin at a high temperature.